Hi Di64
There hasn't been any changes occur to how AccountRight generates ABA files. And once AccountRight generates the ABA file, saving file to computer and overwriting existing files is rather Windows functions.
Overwriting only occurs if the new file has the same name with an existing file at the target location, so I'd suggest double checking the names of the existing files in the directory, as well as the file name used to create the new ABA file. You can always change the older ABA files to a different set of names, then save the new ABA file without overwriting any files, saving the new ABA file to a different directory also stops the overwriting.